The present invention relates to a process for manufacturing a hybrid timepiece component, comprising at least two different materials. It also relates to a timepiece component as such obtained according to this process, a timepiece movement and a timepiece comprising such a hybrid timepiece component.
It is known to manufacture hybrid timepiece components composed, for example, of a first part made of silicon, or more generally made of any micromachinable material, and of a second part made of metal. One process for manufacturing such a hybrid timepiece component uses a first process for manufacturing by micromachining, in particular by deep reactive-ion etching (DRIE), in order to form the first part, and a second manufacturing process based on electroforming, in particular known under the acronym LIGA, in order to grow the second part made of metal. This second metal part may be added a posteriori but it is more accurate to grow it directly in combination with the first part made of silicon.
Document EP 1 932 804 describes, for example, a method for manufacturing such an hybrid timepiece component that comprises the etching of a silicon wafer placed on a working substrate, on which a layer of photoresist will then be deposited, forming a mold for the growth of an electroformed metal layer. The silicon wafer comprises at least one through-cavity which is also filled in by the electroformed metal. This technique provides the advantage of guaranteeing the precision of positioning of the two different materials of the timepiece component. The result of this is therefore a timepiece component which comprises a first level partially made of silicon and partially made of metal and a second level made of metal, superposed on the upper surface of the first level. An “intimate” bond between the two different materials of the component obtained is ensured by the growth of the metal part along the sides of the silicon, at the through-cavity of the first level. However, this bond is neither a chemical bond nor mechanically strong, since it is only based on the roughness alone of these sides, which may prove too weak to ensure the cohesion of the assembly when it is subjected to certain stresses or to a large temperature variation. Thus, the timepiece components thus obtained exhibit a risk of cohesive failure between the two materials, that is to say at the bond between the metal and silicon.
In order to overcome these drawbacks, document WO 2009/062943 describes a process for manufacturing a silicon-metal hybrid component, wherein the metal part sandwiches the silicon part. For this, the manufacturing process carries out two separate steps of growth of the metal part, respectively on each upper and lower surface of the silicon part. This approach improves the cohesion between the two parts of the timepiece component made of different materials. However, it requires the use of a complex manufacturing process, in particular due to the obligation to turn over the substrate in order to carry out the growth on the lower surface of the silicon part. In addition, a weakness is furthermore observed at the interface between the various separate layers of metal formed by the two separate steps of growth of the metal part.